Watch and Clock Escapements eBook

We have spoken of paper being employed for drawings,
but for very accurate delineations we would recommend
the horological student to make drawings on a flat
metal plate, after perfectly smoothing the surface
and blackening it by oxidizing.

PALLET-AND-FORK ACTION.

By adopting eight and one-half degrees pallet-and-fork
action we can utilize ten and one-half degrees of
escape-wheel action. We show at A A’,
Fig. 9, two teeth of a ratchet-tooth escape wheel reduced
one-half; that is, the original drawing was made for
an escape wheel ten inches in diameter. We shall
make a radical departure from the usual practice in
making cuts on an enlarged scale, for only such parts
as we are talking about. To explain, we show
at Fig. 10 about one-half of an escape wheel one eighth
the size of our large drawing; and when we wish to
show some portion of such drawing on a larger scale
we will designate such enlargement by saying one-fourth,
one-half or full size.

[Illustration: Fig. 9]

At Fig. 9 we show at half size that portion of our
escapement embraced by the dotted lines d,
Fig. 10. This plan enables us to show very minutely
such parts as we have under consideration, and yet
occupy but little space. The arc a, Fig.
9, represents the periphery of the escape wheel.
On this line, ten and one-half degrees from the point
of the tooth A, we establish the point c
and draw the radial line c c’. It
is to be borne in mind that the arc embraced between
the points b and c represents the duration
of contact between the tooth A and the entrance
pallet of the lever. The space or short arc c
n represents the “drop” of the tooth.

This arc of one and one-half degrees of escape-wheel
movement is a complete loss of six and one-fourth
per cent. of the entire power of the mainspring, as
brought down to the escapement; still, up to the present
time, no remedy has been devised to overcome it.
All the other escapements, including the chronometer,
duplex and cylinder, are quite as wasteful of power,
if not more so. It is usual to construct ratchet-tooth
pallets so as to utilize but ten degrees of escape-wheel
action; but we shall show that half a degree more can
be utilized by adopting the eight and one-half degree
fork action and employing a double-roller safety action
to prevent over-banking.

[Illustration: Fig. 10]

From the point e, which represents the center
of the pallet staff, we draw through b the
line e f. At one degree below e f
we draw the line e g, and seven and one-half
degrees below the line e g we draw the line
e h. For delineating the lines e g,
etc., correctly, we employ a degree-arc; that
is, on the large drawing we are making we first draw
the line e b f, Fig. 10, and then, with our
dividers set at five inches, sweep the short arc i,
and on this lay off first one degree from the intersection
of f e with the arc i, and through this
point draw the line e g.